Radical polymerization of isopropyl tert-butyl fumarate and maleate,and characterization of the resulting polymers

Radical polymerization of isopropyl tert-butyl fumarate (iPtBF) and monomer-isomerization radical polymerization of isopropyl tert-butyl maleate (iPtBM) were investigated with 2,2′-azobisisobutyronitrile as initiator in the presence and absence of morpholine (Mor) as isomerization catalyst. It was found that iPtBF gave high molecular weight polymers in high yield as previously observed for diisopropyl fumarate (DiPF) and di-tert-butyl fumarate (DtBF). It was confirmed that iPtBF produced by in situ monomer isomerization of iPtBM homopolymerized to give a polymer. Radical copolymerization of iPtBM with styrene in the presence and absence of Mor was also performed and monomer reactivity ratios obtained were compared. From the kinetic study of the isomerization of iPtBM, it was revealed that the isomerization rate showed first-order dependence on the concentration of iPtBM and Mor, and that the apparent activation energy was 29.4 kJ/mol. On pyrolysis of the poly(iPtBF) at 180°C, isobutene and isopropanol were eliminated rapidly to yield polymer containing carboxyl groups and anhydrides. The pyrolytic behavior was different from that of a copolymer of DiPF with DtBF.     

Preparation of functional polymers by living anionic polymerization: Polymerization of allyl methacrylate

The anionic polymerization of allyl methacrylate was carried out in tetrahydrofuran, both in the presence and in the absence of LiCl, with a variety of initiators, at various temperatures. It was found that (1,1-diphenylhexyl)lithium and the living oligomers of methyl methacrylate and tert-butyl methacrylate are suitable initiators for the anionic polymerization of this monomer. The temperature should be below −30°C, even in the presence of LiCl, for the living polymerization to occur. When the polymerization proceeded at −60°C, in the presence of LiCl, with (1,1-diphenylhexyl)-lithium as initiator, the number-average molecular weight of the polymer was directly proportional to the monomer conversion and monodisperse poly(allyl methacrylate)s with high molecular weights were obtained. ¹H-NMR and FT-IR indicated that the α CC double bond of the monomer was selectively polymerized and that the allyl group remained unreacted. The prepared poly(allyl methacrylate) is a functional polymer since it contains a reactive CC double bond on each repeating unit. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2901–2906, 1997     

Role of chain transfer in heterogeneous polymerization of ethylene

The role of chain transfer was studied for the radiation-induced polymerization of ethylene in precipitating media, namely n-butyl alcohol, tert-butyl alcohol and their mixtures. The affinities of those solvents for polyethylene are similar, but the chain-transfer coefficient of n-butyl alcohol is larger than that of tert-butyl alcohol. The polymerizations were carried out in a reactor of 100 ml under a pressure of 300 kg/cm², at 60°C, dose rate of 3.07 × 10⁴–1.75 × 10⁵ rad/hr in the presence of 50 ml of solvents. The polymerization in tert-butyl alcohol shows the kinetic behavior characteristic of a heterogeneous polymerization, such as rate acceleration, high dose rate dependence of polymerization rate, and low dose rate dependence of polymer molecular weight, whereas the polymerization in n-butyl alcohol does not exhibit such behavior and gives polymer having a molecular weight much lower than that of polymer obtained in tert-butyl alcohol. The polymer formed in tert-butyl alcohol exhibits a bimodal molecular weight distribution measured by gel permeation chromatography. In mixed tert-butyl alcohol and n-butyl alcohol solvent, with increasing fraction of n-butyl alcohol, the two peaks not only shift to lower molecular weight but the higher molecular weight peak becomes relatively small. Eventually, the polymer formed in n-butyl alcohol exhibits a unimodal distribution. Those results are well explained on the basis of the proposed scheme for heterogeneous polymerization.     

Novel miktofunctional initiator for the preparation of an ABC‐type miktoarm star polymer via a combination of controlled polymerization techniques

An ABC‐type miktoarm star polymer was prepared with a core‐out method via a combination of ring‐opening polymerization (ROP), stable free‐radical polymerization (SFRP), and atom transfer radical polymerization (ATRP). First, ROP of ϵ‐caprolactone was carried out with a miktofunctional initiator, 2‐(2‐bromo‐2‐methyl‐propionyloxymethyl)‐3‐hydroxy‐2‐methyl‐propionic acid 2‐phenyl‐2‐(2,2,6,6‐tetramethyl‐piperidin‐1‐yl oxy)‐ethyl ester, at 110 °C. Second, previously obtained poly(ϵ‐caprolactone) (PCL) was used as a macroinitiator for SFRP of styrene at 125 °C. As a third step, this PCL–polystyrene (PSt) precursor with a bromine functionality in the core was used as a macroinitiator for ATRP of tert‐butyl acrylate in the presence of Cu(I)Br and pentamethyldiethylenetriamine at 100 °C. This produced an ABC‐type miktoarm star polymer [PCL–PSt–poly(tert‐butyl acrylate)] with a controlled molecular weight and a moderate polydispersity (weight‐average molecular weight/number‐average molecular weight < 1.37). The obtained polymers were characterized with gel permeation chromatography and ¹H NMR. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4228–4236, 2004     

Synthesis of tert-butyl-substituted poly (ether ketone) by nickel-catalyzed coupling polymerization of aromatic dichloride

tert-Butyl substituted poly (aryl ether ketone)s with relatively high molecular weights were prepared by the Ni-catalyzed polymerization of tert-butyl substituted aromatic dichlorides containing ether ketone unit. These polymers were amorphous and soluble in common organic solvents, such as THF, dichloromethane, and chloroform. De-tert-butylation of the polymer by the treatment of trifluoromethanesulfonic acid in the presence of toluene proceeded smoothly and produced crystalline poly (aryl ether ketone). © 1994 John Wiley & Sons, Inc.     

Synthesis of substituted polymethylenes by radical polymerization of alkyl N,N-dialkylfumaramates and maleamates: Relative reactivity of the isomers

Bulk polymerization of alkyl N,N-dialkylfumaramates (FAE) and maleamates (MAE) was performed in the presence of a radical initiator. It has been found that FAE is more reactive than MAE when the reactivity of the two geometrical isomers was compared for their homo- and copolymerizations. From investigation on the effect of ester and N-substituents of these monomers, it has been found that the isopropyl ester shows a higher reactivity than the methyl ester and that N-ethyl and n-butyl substitution gives polymers with high molecular weight of more than several thousands. The resulting substituted polymethylenes from FAE and MAE were characterized and compared with each other. The isomerization of MAE to FAE with morpholine as an isomerization catalyst and monomer-isomerization radical polymerization were also investigated.     

Photo-controlled/living radical polymerization of tert-butyl methacrylate in the presence of a photo-acid generator using a nitroxide mediator

The photo-controlled/living radical polymerization of tert-butyl methacrylate was performed using a (2RS,2′RS)-azobis(4-methoxy-2,4-dimethylvaleronitrile) initiator and a 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO) mediator in the presence of a (4-tert-butylphenyl)diphenylsulfonium triflate photo-acid generator. The bulk polymerization was carried out at 25 °C by irradiation with a high-pressure mercury lamp. Whereas the polymerization in the absence of MTEMPO produced a broad molecular weight distribution, the MTEMPO-mediated polymerization provided a polymer with a comparatively narrow molecular weight distribution around 1.4 without elimination of the tert-butyl groups. The living nature of the polymerization was confirmed on the basis of the linear correlations for the first-order time–conversion plots and conversion–molecular weight plots in the range below 50% conversion. The block copolymerization with methyl methacrylate also supported the livingness of the polymerization based on no deactivation of the prepolymer.     

Preparation of polyethylene block copolymers by a combination of postmetallocene catalysis of ethylene polymerization and atom transfer radical polymerization

The synthesis of block copolymers consisting of a polyethylene segment and either a poly(meth)acrylate or polystyrene segment was accomplished through the combination of postmetallocene-mediated ethylene polymerization and subsequent atom transfer radical polymerization. A vinyl-terminated polyethylene (number-average molecular weight = 1800, weight-average molecular weight/number-average molecular weight =1.70) was synthesized by the polymerization of ethylene with a phenoxyimine zirconium complex as a catalyst activated with methylalumoxane (MAO). This polyethylene was efficiently converted into an atom transfer radical polymerization macroinitiator by the addition of α-bromoisobutyric acid to the vinyl chain end, and the polyethylene macroinitiator was used for the atom transfer radical polymerization of n-butyl acrylate, methyl methacrylate, or styrene; this resulted in defined polyethylene-b-poly(n-butyl acrylate), polyethylene-b-poly(methyl methacrylate), and polyethylene-b-polystyrene block copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 496–504, 2004     

Radical polymerization of alkyl crotonates as 1,2-disubstituted ethylenes leading to thermally stable substituted polymethylene

Radical polymerization of several alkyl crotonates (RCr) was carried out in bulk or in benzene in the presence of radical initiators. Homopolymerization of RCr bearing bulky ester alkyl groups, e.g. tert-butyl (tBCr), 1-adamantyl (AdCr), and 3,5-dimethyl-1-adamantyl crotonate (DMAdCr) proceeded to give a polymer with molecular weight of several thousands despite of the steric hindrance and chain transfer by the presence of the β-methyl group, while the methyl and ethyl esters gave no polymer. The kinetics of the polymerization was examined in detail and absolute rate constants were evaluated by means of electron spin resonance spectroscopy. The propagation rate constants of RCr were 0.41–1.0 L/mol s, being much smaller than those of the corresponding methacrylates (530–570 L/mol s). The termination rate constants were also determined from the analyses of steady state and non-steady state polymerizations. Radical copolymerizations of AdCr (M₂) with several vinyl monomers (M₁) were carried out in bulk at 60°C and the rate constants for cross propagations were calculated to examine reactivities of the monomer and its polymer radical. The structure and thermal properties of the resulting poly (AdCr) were also investigated. Onset temperature of decomposition and glass transition temperature of poly(AdCr) were revealed to be much high as 302 and 234°C, respectively. © 1994 John Wiley & Sons, Inc.     

Cyclodextrins in Polymer Synthesis: Free Radical Polymerization of a tert-Butylmethacrylate-Cyclodextrin Host–Guest System in Aqueous Medium

The homopolymerization of methylated-β-cyclodextrin (me-β-CD) host–guest compound of tert-butyl methacrylate (1a) is described. We investigated the free radical polymerization of the complexed monomer (1a) and of the free monomer (1) at ambient and high temperature. Poly(tert-butylmethacrylate) synthesized via the cyclodextrin mediated method exhibited number-average molecular weights ranging from 12,000–60,000 g/mol with polydispersities from 1.9–3.1. The polymerizations without cyclodextrin show significantly lower yields in comparison with the cyclodextrin mediated polymerizations. Here, the polymer obtained is colloidal dispersed. At ambient temperature (20°C) no polymerization occurs in the absence of cyclodextrin, whereas, under the same conditions, the homopolymerization of the complexed monomer (1a) leads to polymerization with yields around 75%.     

Facile synthesis of AB2‐type miktoarm star polymers through the combination of atom transfer radical polymerization and ring‐opening polymerization

A novel miktofunctional initiator ( 1 ), 2‐hydroxyethyl 3‐[(2‐bromopropanoyl)oxy]‐2‐{[(2‐bromopropanoyl)oxy]methyl}‐2‐methyl‐propanoate, possessing one initiating site for ring‐opening polymerization (ROP) and two initiating sites for atom transfer radical polymerization (ATRP), was synthesized in a three‐step reaction sequence. This initiator was first used in the ROP of ?‐caprolactone, and this led to a corresponding polymer with secondary bromide end groups. The obtained poly(?‐caprolactone) (PCL) was then used as a macroinitiator for the ATRP of tert‐butyl acrylate or methyl methacrylate, and this resulted in AB₂‐type PCL–[poly(tert‐butyl acrylate)]₂ or PCL–[poly(methyl methacrylate)]₂ miktoarm star polymers with controlled molecular weights and low polydispersities (weight‐average molecular weight/number‐average molecular weight < 1.23) via the ROP–ATRP sequence. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2313–2320, 2004     

Effect of alcohols on the gamma-radiation-induced polymerization of ethylene

Gamma-radiation-induced polymerization of ethylene in alcohols such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, and n-pentyl alcohols was carried out under a pressure of 400 kg./cm.²at 30°C. at a dose rate of 1.4 × 10⁵ rad/hr. in a batch reactor of 100 ml. capacity. The yield and molecular weight of polymer formed in the alcohols (except tert-butyl alcohol) were much lower than those of the bulk polymerization under the same conditions, whereas the addition of tert-butyl alcohol increased the yield and reduced the molecular weight. From the infrared spectra of the polymers and those of the bromination products it was concluded that only primary OH exists in the polymer formed in methyl alcohol and that both primary and secondary OH are in the polymer formed in other primary alcohols. Both secondary and tertiary OH were observed in the polymer when the secondary alcohols were used, and only tertiary OH in the case of tert-butyl alcohol. These polymers were found to contain small amounts of vinylidene unsaturation and methyl group. On the basis of these results the roles of the alcohols in the polymerization are discussed.     

Complex macromolecular structures from stable radical containing block copolymers

A novel synthetic strategy for the synthesis of graft copolymers is reported. Block copolymers containing segments with stable nitroxyl radicals side groups were first prepared by anionic polymerization, which were then used as a precursor for the subsequent nitroxide-mediated radical polymerization (NMRP) of styrene. This way, block–graft copolymers with polystyrene side chains grafted from one of the blocks were successfully synthesized in a controlled manner. In addition, block–graft copolymers with grafted polystyrene chains and a poly(tert-butyl methacrylate) block were subjected to hydrolysis to yield the corresponding amphiphilic polymers. The structures and the molecular weight characteristics of the polymers were characterized by spectral and chromatographic analyses. The surface morphology of thus obtained polymers was also investigated by microscopic techniques. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 62–69     

Hydrophilic graft modification of a commercial crystalline polyolefin

Hydroxy‐functionalized isotactic poly(1‐butene) was synthesized using transition metal‐catalyzed regioselective C? H borylation at the side chain of the commercial polyolefin and subsequent oxidation of the boronic ester functionality. Functionalization up to ～ 19 mol % of the termini of the ethyl side chain occurred without significant side reactions that could alter the polymer chain length. Esterification of the hydroxy group in the polymer with 2‐bromoisobutyl bromide generated a side chain‐functionalized polyolefin macroinitiator. Atom transfer radical polymerization of tert‐butyl acrylate from the macroinitiator produced a high molecular‐weight graft copolymer of the polyolefin, isotactic poly(1‐butene)‐graft‐poly(tert‐butyl acrylate) (PB‐g‐PtBA). Finally, the hydrolysis of the tert‐butoxy ester group of PB‐g‐PtBA created an amphiphilic polyolefin, isotactic poly(1‐butene)‐graft‐poly(acrylic acid), which contained a short carboxylic acid‐functionalized polymer block at the side chain. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3533–3545, 2008     

The effect of radical trapping reagents upon formation of poly(α-tetrahydrothiophenio para-xylylene) polyelectrolytes by the wessling soluble precursor method

Molecular weights were studied by gel permeation chromatography of derivatized poly(α-tetrahydrothiophenio para-xylylene) chloride produced by aqueous or methanolic base-induced polymerization of 1,4-bis(tetrahydrothiopheniomethyl) benzene dichloride, both with and without a variety of added polymerization inhibiting agents. Efficient radical scavenging agents such as 2,2,6,6-tetramethylpiperidinoxyl and hydrogen atom donor 2,4,6-tri-tert-butylaniline reduced the degree of polymerization of the reactive α-(tetrahydrothiophenium chloride)-para-xylylene intermediate produced in this chemistry, and in some cases completely suppressed formation of high polymer. These two traps did not affect the equilibrium production of the para-xylylene by UV-Vis spectral analysis; hence they must affect the subsequent polymerization chain propagation steps in the mechanism. Electron spin resonance studies of polymerization in the presence of 0.00025 equiv of TEMPO showed disappearance of the spin label, a result consistent with a radical scavenging process. The results suggest that production of high molecular weight poly(α-tetrahydrothiophenio para-xylylene) chloride proceeds through a radical chain propagation sequence. © 1992 John Wiley & Sons, Inc.     

Initiation of radical polymerization by peroxyacetates: Polymer end-group analysis by electrospray ionization mass spectrometry

End-groups of poly(methyl methacrylate) from radical solution polymerization of MMA using tert-butyl peroxyacetate (TBPA), tert-amyl peroxyacetate (TAPA), 1,1,2,2- tetramethylpropyl peroxyacetate (TMPPA), and 1,1,3,3-tetramethylbutyl peroxyacetate (TMBPA) as the initiators were analyzed via electrospray ionization mass spectrometry (ESI-MS). The type and the relative concentration of the radical species, which actually initiate macromolecular growth, are determined. In the majority of cases, these species differ from the primary radicals from thermal decomposition of the peroxyacetates. Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was applied for unambiguous peak assignment. The methylcarbonyloxyl radical, which is formed by the decomposition of all peroxyacetates, was found to undergo decarboxylation yielding an initiating methyl radical. TAPA- and TMPPA-derived alkoxyl radicals mainly show β-scission, TMBPA-derived alkoxyl radicals additionally undergo a 1,5-hydrogen-shift reaction. The tert-butoxyl radicals produced from TBPA undergo pronounced chain-transfer reaction prior to their decomposition into methyl radicals and acetone. In the case of using benzene as a relatively inert solvent, the tert-butoxyl radicals exhibit transfer to monomer yielding polymer molecules, which do not carry any initiator-derived end-groups. By using mesitylene as a cosolvent, small amounts of star polymer were generated via multiple hydrogen abstraction by tert-butoxyl radicals from the three individual methyl groups of mesitylene. This uncomplicated procedure of modification of end-group and polymer topology may be attractive for facile adjustment of polymer viscosity in technical processes. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2453–2467, 2007     

Kinetics of the gamma-radiation-induced polymerization of ethylene in tert-butyl alcohol

The gamma-radiation-induced polymerization of ethylene in the presence of 13–30 ml of tert-butyl alcohol was carried out under a pressure of 120–400 kg/cm² at a dose rate of 1 × 10³ to 2.5 × 10⁴ rad/hr at 30°C with a 100 ml reactor. The polymerization rate and the molecular weight of the polymer increased with reaction time and pressure and decreased with amount of tert-butyl alcohol. The polymer yield increased almost proportionally with the dose rate, while the molecular weight was almost independent of it. These results were graphically evaluated, and the rate constants of initiation, propagation, and termination for various conditions were determined. No transfer was observed. On the basis of these results the role of tert-butyl alcohol in the polymerization is discussed.     

Effect of monomer hydrophilicity on ARGET–ATRP kinetics in aqueous mini-emulsion polymerization

Activators regenerated by electron transfer (ARGET) atom transfer radical polymerization (ATRP)-based aqueous miniemulsion polymerization where the polymerization takes place in the stabilized monomer droplets is described. In this work, we compared styrene, n-butyl methacrylate (nBMA) and tert-butyl methacrylate (tBMA) and investigated the influence of their hydrophobicity on dispersity, molecular weight and particle stability based their partition coefficients (logP) (2.67, 2.23, and 1.86, respectively). Tetrabutylammonium bromide (TBAB) was used as a phase transfer agent for the controlled delivery of Cu²⁺-Br/tris(2-pyridylmethyl)amine (TPMA), a hydrophilic catalyst, into monomer droplets of varying hydrophobicity. The resulting dispersity and particle stability of each polymer is a function of its logP value, with the most hydrophobic monomer (styrene) displaying the narrowest dispersity and most control (Đ < 1.3), and the most hydrophilic polymer poly(tert-butyl methacrylate) (PtBMA) having reduced emulsion stability, determined by the observation of aggregate formation. Selected polymerization parameters, including effects of total ascorbic acid feed concentration and the monomer concentration and their effects on dispersity are reported. The controlled polymerizations of hydrophilic monomers using ARGET-ATRP in miniemulsion conditions and understanding the effect of monomer hydrophilicity on the emulsion stability will broaden the use of ARGET-ATRP in emulsion polymerization for the synthesis of polymer-grafted nanoparticles with hydrophilic corona.     

A novel scheme of heterogeneous polymerization of ethylene

The heterogeneous polymerization of ethylene initiated by radiation in tert-butyl alcohol was studied. The polymerization was carried out in a 100-ml reactor at 25–100°C and pressures of 200–300 kg/cm² in the presence of 50 ml of tert-butyl alcohol containing 7 wt-% water. The amounts of polymerized monomer, the average molecular weight of polymer formed, and the molecular weight distribution of polymer were measured at various stages of reaction and at various temperatures. The molecular weight distribution was found to be very much dependent on the reaction time and temperature. For the polymer formed at 50–60°C in the very early stages of reaction, the molecular weight distribution is unimodal, and in the intermediate stage a shoulder appears at a molecular weight higher than the first peak which increases as the polymerization proceeds; eventually a bimodal curve is formed. The bimodal distribution curves were analyzed to determine the fractions and average molecular weights of the each peak. On the basis of these data for the molecular weight distribution and kinetic behavior, a new scheme for the heterogeneous polymerization is proposed which indicates that the polymerization proceeds via propagating radicals in two different physical states, namely, loose and rigid states.     

Effect of temperature on the radiation-induced polymerization of ethylene in various media

The effects of temperature on the radiation-induced polymerization of ethylene in bulk and in the presence of ethyl alcohol, n-butyl alcohol, tert-butyl alcohol, cyclohexane, 2,2,4-trimethylpentane, and 2,2,5-trimethylhexane were studied. The changes of the amounts of polymerized monomer with the reaction temperature were different from each other in these reaction systems, especially in the range lower than 60–80°C. At temperatures lower than 60–80°C, as the reaction temperature increases, the amount of polymerized monomer decreased in bulk and in the presence of tert-butyl alcohol. The amount was almost constant in the presence of ethyl alcohol and 2,2,4-trimethylpentane, and it increased in the presence of n-butyl alcohol, cyclohexane, and 2,2,5-trimethylhexane. However, in the temperature range higher than 60–80°C, the amount of polymerized monomer increased with increasing temperature in every reaction system except for bulk polymerization. The molecular weight of polymer decreased with increasing temperature in every reaction system except at temperatures lower than 25°C. The molecular weight of polymer formed in bulk, in tert-butyl alcohol, and also in 2,2,4-trimethylpentane were relatively higher than that in other reaction systems. A bimodal molecular weight distribution was observed for the polymer formed in bulk and in tert-butyl alcohol at 40–60°C. These results are discussed in connection with the heterogeneity of the reaction system. The differences due to temperature in each reaction system are explained as due to the difference in affinity of the reaction system for the propagating chain and in the facility of chain transfer to the medium.